1. Field of the Invention
The present invention relates, to a magnetic head and a method of manufacturing, the same and, more particularly, to a magnetic head having a magnetic core with small track width and gap distance which can perform the high density recording and reproduction and to a method of manufacturing the same.
2. Description of the Prior Art
A process for manufacturing a magnetic core of this kind according to a so-called conventional confronting method will be first described with reference to FIGS. 1A to 1E. In the first step, an ingot 1 consisting of magnetic material such as ferrite or the like as shown in FIG. 1A is cut and ground, thereby to obtain a block 2 as shown in FIG. 1B. Furthermore, a winding window 3 like a long groove as shown in FIG. 1C is formed in this block 2, then it is ground to obtain a gap surface 4 serving as a confronting surface at which a magnetic gap will be formed later and is smoothly finished.
Then, as shown in FIG. 1D, such two blocks 2 and 2' which were subjected to the above-described processings are confronted so that a gap spacer 5 consisting of non-magnetic material such as SiO.sub.2 or the like is sandwiched by their gap surfaces 4, and thereafter they are joined using an adhesive agent, glass, or the like.
Subsequently, the blocks 2 and 2' are cut at regular intervals along the direction perpendicular to their axial directions, then each sliced assembly is further subjected to the finishing abrasion processing, so that a magnetic core unit 6 as shown in FIG. 1E is completed. In this case, a magnetic gap 6b is formed by the portion where the gap spacer 5 was sandwiched between the respective gap surfaces 4 of half-unit cores 6a and 6a which are half bodies of the magnetic core unit.
However, according to the foregoing confronting method, the gap surface 4 of the half-unit core 6a is formed due to the mechanical processing such as the grinding, cutting, abrasion, etc., so that this causes a deformation due to the processing or a notch at the corner. Due to this, it is difficult to process the device in highly accurate manner so that a width of the gap surface 4, i.e., a magnetic gap width, becomes small. Moreover, it is difficult to present the flatness of the gap surface 4 with, high degree of accuracy. In addition, since an adhesive agent is interposed for joining, a distance between the mutual gap surfaces 4, i.e., a distance of the magnetic gap will have increased.
Due to the above reasons, according to the foregoing structure and manufacturing method, it was difficult to mass-produce magnetic cores in which a magnetic gap width, i.e., a track width, is 30 .mu.m or less and a distance of the magnetic gap is about 0.3-1.0 .mu.m.
There will be now described another conventional process for manufacturing a magnetic head which has been proposed to solve such problems with respect to FIGS. 2A to 2I.
A thin film of soft magnetic material such as Sendust, amorphous, or the like is formed as shown in FIG. 2B on the surface of a substrate 7 consisting of non-magnetic material such as crystallized glass or the like as shown in FIG. 2A by means of sputtering or the like, thereby to obtain a magnetic material layer 8.
Then, after another substrate 7' consisting of non-magnetic material which is not covered by the magnetic material layer 8 was overlapped on the layer 8, they are adhered by crystallized glass or adhesive agent or the like. Subsequently, it is cut along the lines A--A and B--B shown in FIG. 2C to obtain rectangular parallelopiped blocks.
Next, these blocks are piled as shown in FIG. 2D and are mutually joined by an adhesive agent to form a lamination body 9. This lamination body 9 is further cut along the line C--C to obtain two lamination blocks 9a shown in FIG. 2E.
Then, a long groove like winding window 10 is formed in one lamination block 9a' between such two blocks by grinding or the like as shown in FIG. 2F. Furthermore, a gap surface 11 serving as a confronting surface to form a magnetic gap and H) the confronting surface are ground and are smoothly finished.
Next, as shown in FIG. 2G, a thin layer 12 of non-magnetic material such as silica SiO.sub.2 or the like is formed on the gap surface 11 by way of sputtering or the like.
On the other hand, the confronting surface of the lamination block 9a of FIG. 2E is ground and finished. This confronting surface thus finished and the gap surface 11 onto which the non-magnetic material layer 12 was formed and the confronting surface of the lamination block 9a' are aligned in position and are confronted so that their corresponding magnetic material layers 8 face and coincide with one another. Then, they are adhered by an adhesive agent or the like to obtain a core lamination block 13 shown in FIG. 2H.
Such core lamination blocks 13 are laminated and at the portion of the substrate 7, they are cut in the direction parallel to the laminating direction so that each piece has a predetermined thickness. Thereafter, such a piece is ground and finished, so that a magnetic core unit 14 shown in FIG. 2I is completed. In this case, a magnetic gap 16 is formed through the thin non-magnetic material layer 12 between the confronting edge surfaces at the gap surfaces of the respective magnetic material layers 8 and 8 of half-unit cores 15 and 15' which are the half units of the magnetic core 14.
According to the above-described manufacturing method and structure, a thickness of the magnetic material layer 8 becomes a track width and a thickness of the thin non-magnetic material layer 12 becomes a distance of the magnetic gap; therefore, it is possible to produce a track width and a magnetic gap distance becomes small.
However, since the gap surface 11 is formed by being cut and the confronting surface and gap surface are joined by an adhesive agent or because of other similar reasons, there occur problems such as a deformation due to the processing, a diffusion of the adhesive agent, and the like similarly as in the case mentioned before, so that this causes the distance of the magnetic gap to be increased.
In addition, in this method, when the lamination blocks 9a and 9a' are confronted and joined, they have to be aligned in position so that the edge surfaces of the magnetic material layers 8 and 8 can accurately coincide and face. However, since a thickness of the magnetic material layer 8 is about 30 .mu.m, this positioning is very difficult and the dislocation, i.e., so-called track shift will be easily caused.
That is, it was difficult to mass-produce magnetic cores having a very small track width and gap distance with a high degree of accuracy even by the foregoing structure and method.
A structure and method for manufacturing a magnetic core to solve such problems have been proposed in Japanese Patent Application Laid-Open Publication No. 73913/80.
According to this proposition, a winding window 18 serving as a throughhole is formed in a core-shaped substrate 17 consisting of non-magnetic material such as glass or the like as shown in FIG. 3. Furthermore, a thin film of soft magnetic material such as Sendust or the like is formed by means of sputtering or the like on, for example, the left half region of the side surface shown to obtain a magnetic layer, and thereafter a thin film of non-magnetic material is formed on a magnetic gap forming portion above the winding window 18 of the side surface of that magnetic layer. Subsequently, a thin film of soft magnetic material such as Sendust or the like is coated entirely on the same side surface and the same whole side surface is ground, thereby to obtain a magnetic core.
With such a structure, a thickness of the thin film of soft magnetic material becomes a gap while a thickness of the thin film of non-width magnetic material becomes a magnetic gap distance. In addition, both said thin films and the magnetic gap are formed not by mechanical processing but by sputtering or the like. Thus, a width and a distance of the magnetic gap can be accurately processed to be small.
However, in this structure, in the case where a magnetic gap width is so narrow to be, e.g., 20 .mu.m or less, the recording and reproducing characteristics of the magnetic core are largely influenced due to a shape and a dimension of the winding window 18; therefore, the winding window 18 needs to be formed with a high degree of accuracy.
As an example, the winding window 18 has to be formed so that .theta..sub.1 =60.degree., L.sub.1 =0.4 mm, and L.sub.2 =0.35 mm in FIG. 3.
On the, other hand, the non-magnetic substrate 17 needs to be made of such material that its coefficient of thermal expansion is identical to that of the thin film layer of high permeability material to be formed on the substrate 17 and so that it can easily slide and follow on a recording medium such as a magnetic tape or the like and that it further has an excellent abrasion resistance. Although there is a partially crystallized glass or the like as such material, it is very difficult to form very accurately the winding window serving as the through hole in the substrate 17 consisting of such material and therefore it is impossible to realize a low cost.
On one hand, in the magnetic core of the magnetic head for recording and reproducing at high density, the necessary characteristics differ in dependence upon its portion and there is no magnetic material which can satisfy all of the characteristics. Therefore, it has been confirmed that better characteristics can be derived as a whole if the magnetic core is constituted by combining different magnetic materials in accordance with the necessity of the characteristic which differs depending upon the portion. For instance, for the portion of the magnetic core to come into contact with the slide surface of the recording medium, it is suitable to use magnetic material such as Sendust alloy, amorphous material, or the like which has a high saturation magnetic flux density, low coercive force and excellent abrasion resistance. In addition, for the other portions of the magnetic core, it is proper to use magnetic material such as ferrite or the like which has a large electrical resistance and excellent high frequency response. The combination of both of them can present overall better characteristics.
However, according to the proposed structure mentioned above, since the magnetic material portion which forms the whole magnetic path is formed by one kind of continuous magnetic material layer, the high characteristics cannot be derived due to the foregoing reasons.